A conventional automatic clutch control apparatus discloses a technology in which an engine rotation speed is approximated to the rotation speed of the input shaft of the transmission apparatus for establishing a synchronized rotation therebetween with a predetermined speed change rate to restrain a possible shock generated upon clutch engagement. In this case, change speed of the engine rotation can be controlled by setting a predetermined target clutch transmitting torque. The clutch transmitting torque is variable depending on the clutch engagement ratio (engagement amount) and accordingly, the operation amount of the clutch actuator is controlled to adjust such variable clutch transmitting torque.
For example, according to a conventional apparatus disclosed in JP1998-318288 A, clutch engagement amount reference value is set to obtain a target transmitting torque based on the throttle opening degree and the vehicle speed. According to another conventional apparatus disclosed in JP1997-112589 A, the clutch engagement amount reference value is set to obtain a target transmitting torque based on the throttle opening degree, rotation speed of the driving shaft of the engine and the rotation speed of the input shaft of the transmission apparatus. This target transmitting torque is obtained by first, calculating a target inertia torque which is obtained by multiplying engine inertia by an engine target rotation speed change rate and then subtracting the obtained target inertia torque from the engine current state output torque.
In the conventional automatic clutch control apparatus as described above, the clutch engagement amount reference value is set to obtain the clutch target transmitting torque, based on the information, such as the throttle opening degree, rotation speed of the driving shaft of the engine, the rotation speed of the input shaft of the transmission mechanism and the vehicle speed, but not based on the vehicle condition, such as under the vehicle running straight forward or a vehicle in turning and the speed change (gear shifting) operation is performed based on the clutch engagement reference value. Accordingly, when a speed change operation is performed under the vehicle being turning to right or left or making a winding, an operator of the vehicle may feel susceptibly the clutch engagement operation more than the operator feels when the vehicle is running straight forward.
For example, when a speed change operation is performed under the vehicle being turning to the right or the left, the operator being cautiously driving the vehicle at a low vehicle speed, if the clutch engagement is performed with the same engagement amount reference value as the time when the vehicle is running straight forward, the vehicle behavior such as pitching motion, may be affected due to the change in acceleration in a front and rear direction. Such vehicle behavior may bother the operator of the vehicle, which would not be noticed when the vehicle is running straight forward. The operator of the vehicle may desire to perform a more smooth speed change operation under the vehicle being turning at a low speed, than the vehicle being running straight forward.
Further, when a vehicle is turning at a high speed in sporty as winding and the operator wishes to change the speed by gear shifting, if the clutch engagement is carried out with the same engagement amount as the time when the vehicle is running straight forward, the transmitting torque of the clutch between the driving shaft of the engine and the input shaft of the transmission mechanism becomes smaller than the torque desired by the operator. This may give an ill-effect to the operator of the vehicle due to the insufficient direct feeling of speed change operation. In other words, the operator of the vehicle mostly desires to perform a speed change operation with a more direct feeling when the vehicle is turning at a high speed than when the vehicle is running straight forward.